Fuel guage question

[LM44S]

Finally got a chance to work on my truck, grounded the sending unit to the frame with a separate wire and grounded the frame that holds the gauges to the dash with a separate wire also. The gauges read full and according to the manufacturer of the sending unit that indicates a break in the wire to the unit. Ran a jumper wire from the back of the gauge to the sending unit and stiil read full. Not sure what to try, any ideas? Thanks.